Actually, to be a bit of an historical curmudgeon, the December 25 date has more to do with Mithras (
natalis soli invicti) than Yeshua ben Yosef, the son of Miryam and Yosef of Natzaret. He was much more likely to have been born during one of the pilgrim feasts prescibed by the Torah.
The Roman Catholic Church appropriated the date for a variety of reasons around 350 AD. The Eastern bishops never did completely buy into the date. For a source, see the Catholic Encyclopedia .
And how does that change the celebration called "Christmas" that westerners have celebrated every December 25th going back more than a millennium? Does that somehow make it a less legitimate part of our heritage and culture?